Processes and Intermediates for Preparing a Macrocyclic Protease Inhibitor of HCV

ABSTRACT

The present invention relates to the cinchonidine salt 
     
       
         
         
             
             
         
       
     
     useful in the preparation of intermediates for preparing a macrocyclic HCV inhibitor, as well as processes involving this salt.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of prior application Ser. No.13/141,715 filed, Jun. 23, 2011, currently allowed, which claimspriority of the benefits of the filing of PCT Application No.PCT/EP2009/067715, filed Dec. 22, 2009, and European Patent ApplicationNo. EP08172691.1 filed Dec. 23, 2008. The complete disclosures of theaforementioned related applications are hereby incorporated by referencefor all purposes.

FIELD OF THE INVENTION

The present invention relates to synthesis procedures and synthesisintermediates of a macrocyclic protease inhibitor of the hepatitis Cvirus (HCV).

BACKGROUND OF THE INVENTION

Hepatitis C virus (HCV) is the leading cause of chronic hepatitis, whichcan progress to liver fibrosis leading to cirrhosis, end-stage liverdisease, and HCC (hepatocellular carcinoma), making it the leading causeof liver transplantations. Current anti-HCV therapy, based on(pegylated) interferon-alpha (IFN-α) in combination with ribavirin,suffers from limited efficacy, significant side effects, and is poorlytolerated in many patients. This prompted the search for more effective,convenient and better-tolerated therapy.

Replication of the genome of HCV is mediated by a number of enzymes,amongst which is HCV NS3 serine protease and its associated cofactor,NS4A. Various agents that inhibit this enzyme have been described. WO05/073195 discloses linear and macrocyclic NS3 serine proteaseinhibitors with a central substituted proline moiety and WO 05/073216with a central cyclopentyl moiety. Amongst these, the macrocyclicderivatives are attractive by their pronounced activity against HCV andattractive pharmacokinetic profile.

WO 2007/014926 describes macrocyclic cyclopentyl and proline derivativesincluding the compound of formula (I), with the structure representedhereafter. The compound of formula (I) is a very effective inhibitor ofthe HCV serine protease and is particularly attractive due to itsfavorable pharmacokinetical profile. Because of its properties thiscompound has been selected as a potential candidate for development asan anti-HCV drug. Consequently there is a need for producing largerquantities of this active ingredient based on processes that provide theproduct in high yield and with a high degree of purity. WO 2008/092955describes processes and intermediates to prepare the compound of formula(I).

The compound of formula (I) can be prepared starting from anintermediate (VI), wherein the ester function is hydrolysed, yieldingcarboxylic acid (V), which in turn is coupled in an amide formingreaction with the cyclopropyl amino acid (Va). The resultingintermediate (IV) is cyclized by an olefin metathesis reaction in thepresence of a suitable metal catalyst such as e.g. an ylidene Ru-basedcatalyst. The resulting macrocyclic ester (III) is then hydrolyzed tomacrocyclic acid (IV). The latter is coupled with a sulfonylamide (V) inan amide forming reaction to yield the end product (I). These reactionsare outlined in the reaction scheme herebelow. In this and the followingreaction schemes or representations of individual compounds, R isC₁₋₄alkyl, in particular R is C₁₋₃alkyl, more in particular R isC₁₋₂alkyl, or in one embodiment R is ethyl. R¹ is C₁₋₄alkyl, inparticular R¹ is C₁₋₃alkyl, more in particular R¹ is C₁₋₂alkyl, or R¹ ismethyl; or R¹ is ethyl.

Intermediate (VI) in turn can be prepared using procedures described inWO 2008/092955, in particular starting from a hydroxycyclopentylbis-ester of formula (Xa), by either

-   (a) reacting the hydroxycyclopentyl bis-ester of formula (Xa) with a    thiazolyl substituted quinolinol (VII) in an ether forming reaction,    thus obtaining a quinolinyloxycyclopentyl bis-ester of formula    (XII), wherein the benzyl ester group that is in cis position    vis-à-vis the ether group in the quinolinyloxy-cyclopentyl bis-ester    of formula (XII) is selectively cleaved to a mono carboxylic acid    (XI), which in turn is coupled with an alkenylamine in an amide    forming reaction, thus obtaining the desired end product of formula    (VI); or-   (b) selectively converting the hydroxycyclopentyl bis-ester of    formula (Xa) to the mono carboxylic acid (IX), which in turn is    coupled with an alkenylamine in an amide forming reaction to obtain    hydroxycyclopentylamide (VIII), which in turn is reacted with a    thiazolyl substituted quinolinol (VII), thus obtaining the desired    end product of formula (VI); as outlined in the following reaction    scheme:

Each R¹ in the processes represented in the above scheme is as specifiedabove and preferably R¹ is methyl. Bn represents benzyl.

The presence of various chiral centers in the compound of formula (I)and its predecessors poses particular challenges in that chiral purityis essential to have a product that is acceptable for therapeutic use.The intermediate (VI) has three chiral centers and getting the correctstereochemistry for all three centers is an important challenge for anysynthesis processes aimed at preparing this compound. Hence theprocesses for preparing (VI) should result in products of acceptablechiral purity without use of cumbersome purification procedures with theloss of substantial amounts of undesired stereoisomeric forms.

WO 2008/092955 describes a synthesis procedure for intermediate (Xa)starting from 4-oxo-cyclopentyl-1,2-bis-carboxylic acid (XVII) byreducing the keto function to an alcohol, thus obtaining4-hydroxy-cyclopentyl-1,2-bis-carboxylic acid (XVI), which in turn iscyclized to the bicyclic lactone (XV), wherein the carboxylic acid groupin the bicyclic lactone (XV) is esterified with benzyl alcohol thusobtaining the lactone benzyl ester (XIV). The lactone in the latter isopened by a transesterification reaction in the presence of aC₁₋₄alkanol, thus yielding the hydroxycyclopentyl bis-ester of formula(X), which in turn is resolved in enantiomers (Xa) and (Xb); as outlinedin the following reaction scheme:

Each R¹ in the processes represented in the above scheme is as specifiedabove and preferably R¹ is methyl.

A disadvantage of the above process is that it involves a resolution ofthe enantiomers of (X) by chiral column chromatography, a cumbersomeprocedure that is difficult to run at large scale production.

Honda et al., Tetrahedron Letters, vol. 22, no. 28, pp 2679-2682, 1981,describes the synthesis of (±)-brefeldin A using the following startingmaterials:

The synthesis of Honda et al. starts fromdl-trans-4-oxocyclopentane-1,2-dicarboxylic acid 2, which was esterifiedto the corresponding methyl ester 3, and reduced with Raney-Ni to thealcohol 4. Partial hydrolysis of 4 to the monocarboxylic acid andbenzylation with benzyl bromide gave predominantly diastereoisomer 5,namely the diastereoisomer wherein the hydroxy and benzyl ester groupsare in cis position. The latter ester 5 in Honda et al. and compound (X)are both racemates, but are diastereoisomers of each other, moreprecisely epimers on the carbon no. 4 bearing the hydroxy group.Compound (Xa) is one of the two enantiomers obtained by separation fromthe racemic compound (X). The other enantiomer is compound (Xb).

WO 2005/073195 describes the synthesis of enantiomercally pure bicycliclactone (8b) starting from an enantiomer of3,4-bis(methoxycarbonyl)cyclopentanone. The latter was prepared asdescribed by Rosenquist et al. in Acta Chemica Scandinavica 46 (1992)1127-1129. The trans (3R,4R)-3,4-bis(methoxycarbonyl)cyclopentanoneisomer was converted to the bicyclic lactone (8b):

WO 2005/073195 additionally describes further modification of lactone(8b) to the t.Bu ester, opening of the lactone and coupling withappropriately protected amino acids, e.g. with(1R,2S)-1-amino-2-vinylcyclopropane carboxylic acid ethyl ester, whichin the latter instance yields:

The build-up of the compounds of formula (I) necessarily involvesintroducing the thiazolyl substituted quinoline moiety on thecyclopentyl ring via an ether linkage. The Mitsunobu reaction offers anattractive reaction route for preparing aromatic alkylethers in which analkyl ether is activated and reacted with a phenol. In addition,Mitsunobu reactions are in general more efficient than the O-arylationreactions, which require additional synthesis steps. In this mildreaction the stereochemistry of the alkyl part is inverted. The reactiongives rise to side products, such as R′OOC—NH—NH—COOR′, wherein R′ isC₁₋₄alkyl and in particular ethyl or isopropyl, othernitrogen-containing compounds, and triphenylphosphine oxide, which needto be separated from the desired end product.

The processes of the present invention are advantageous in that they aresuitable for large scale production. Cumbersome purification steps, inparticular by chromatography, are avoided. Essential in the synthesis ofthe compound of formula (I) is the built-up of the cyclopentyl moietywith the right stereochemistry at its three chiral centers.

One of the aspects of this invention concerns processes for preparingthe intermediates (VIII) in high yield and purity, especially in termsof chiral purity, that are fit for large scale industrial application.

The present invention is aimed at providing procedures to preparecyclopentyl intermediates with the right stereochemistry, in high yieldand purity. In particular the present invention concerns the preparationof the intermediates

which find use in the procedures to prepare the compound of formula (I).

DESCRIPTION OF THE INVENTION

In one aspect, the present invention relates to a process for preparinga compound of formula (VIII), starting from an cinchonidine salt (XXa),which is reacted with N-methyl-hexenamine (NMHA) (XIX) in anamide-forming reaction to yield the bicyclic lactone amide (XVIII), inwhich the lactone group is opened to yield the desired product (VIII).These reactions are illustrated in the scheme below, wherein R¹ is asspecified above.

In a further aspect the invention concerns the preparation of thecinchonidine salt (XXa), which is obtained by the resolution of thediastereoisomeric salt mixture (XX) by selective crystallization of(XXa). The salt (XX) in turn is obtained by forming the cinchonidinesalt of the racemic bicyclic lactone carboxylic acid (XV), as outlinedin the following reaction scheme:

In still a further aspect, the invention concerns the cinchonidine saltof formula

This salt is useful as intermediate in the preparation of intermediate(VIII), and therefore also in the preparation of the HCV inhibitor (I).

The synthesis procedures of the present invention offer the advantagethat the correct stereochemistry at the cyclopentyl moiety is obtainedand this without using chiral chromatography. The cinchonidine salt(XXa) has been found to selectively crystallize with high chiral purity.

The reaction of the cinchonidine salt (XXa) with NMHA (XIX) is an amideforming reaction, which comprises reacting the starting materials withan amide-coupling reagent in a reaction-inert solvent, optionally in thepresence of a base. Solvents that can be used comprise halogenatedhydrocarbons such as dichloromethane (DCM) or chloroform, ethers such astetrahydrofuran (THF) or 2-methyltetrahydrofuran (MeTHF), alcohols suchas methanol or ethanol, hydrocarbon solvents such as toluene or xylene,dipolar aprotic solvents such as DMF, DMA, acetonitrile, or mixturesthereof. Preferred are dichloromethane, MeTHF, methanol, ethanol,toluene, or mixtures thereof. Amide-coupling agents comprise agents suchas N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ),N-isopropoxycarbonyl-2-isopropoxy-1,2-dihydroquinoline, in particularits hydrochloride salt, (IIDQ),N,N,N′,N′-tetramethyl-O-(7-azabenzotriazol-1-yl)uroniumhexafluorophosphate (HATU),benzotriazol-1-yl-oxy-tris-pyrrolidino-phosphonium hexafluorophosphate(commercially available as PyBOP®), 1,1′-Carbonyldiimidazole (CDI),1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDI or EDCI) as well asits hydrochloride salt, dicyclohexyl-carbodiimide (DCC), or1,3-diisopropylcarbodiimide,O-benzotriazole-N,N,N′,N′-tetramethyl-uronium-hexafluoro-phosphate(HBTU) and the like. A catalyst may be added, for example1-hydroxybenzotriazole (HOBt) or 4-dimethylaminopyridine (DMAP). Thereaction is usually conducted in the presence of a base, in particularan amine base such as a tertiary amine, e.g. triethylamine,N-methylmorpholine, N,N-diisopropylethylamine, (the latter also beingreferred to as Hünig's base, DIPEA, or DIEA). Preferably, no base isused. In one embodiment, the reaction is conducted in DCM or MeTHF withEEDQ, optionally with addition of methanol at the end of the reaction,at reflux temperature of the reaction mixture.

In an alternative embodiment, the salt (XXa) can be split intocinchonidine and the bicyclic lactone, and the latter can be reactedwith NMHA in an amide forming reaction as described above. It has beenfound that the cinchonidine salt (XXa) itself can be used in the amideforming reaction and the cinchonidine can afterwards be removed easilyin the work-up of the reaction mixture, for example by treatment of thelatter with an acid such as HCl, and washing away the side products withaqueous phases.

The lactone functionality in the resulting bicyclic lactone amide(XVIII) is opened by a transesterification reaction with an alcohol,which may also serve as a solvent, in particular a C₁₋₄alkanol such asmethanol or ethanol, in the presence of an acid. Acids that can be usedare strong organic acids such as sulfonic acids, in particularmethanesulfonic acid. A solvent can be added such as an ether, inparticular THF or MeTHF; or hydrocarbon solvents such as toluene orxylene. The transesterification reaction yields the ester of the alcoholthat is used, e.g. when conducting the reaction in methanol, the methylester is formed.

The cinchonidine salt (XX) in turn can be prepared by treating theracemic bicyclic lactone carboxylic acid (XV) with cinchonidine.Typically the racemic salt (XX) is not isolated, but kept in solutionwhile the desired isomer (XXa) is allowed to crystallize. In oneembodiment, a suspension of cinchonidine is added to a solution of (XV)at slightly elevated temperature and subsequently allowing the mixtureto cool whereupon the desired salt (XXa) crystallizes. Furtherpurification may comprise recrystallization. Suitable solvents fordissolving (XV) include ester solvents such as ethyl acetate, whereassuitable solvents for the cinchonidine supension include acetonitrile.In one embodiment the salt formation is done at a temperature of about50 to about 70° C., in particular at about 60° C., and the mixture isallowed to cool to about room temperature, such as a temperature in therange from about 20 to about 25° C., e.g. at about 22° C. Furtherpurification can be done by recrystallization from an appropriatesolvent or solvent mixture, in particular an alcohol such as aC₁₋₄alkanol, e.g. isopropanol, or by re-slurrying in a solvent orsolvent mixture, e.g. an ethanol/water mixture such as a 5%/95% (w/w)water/ethanol mixture.

The finding that the salt (XXa) can be isolated by crystallizationprovides an elegant way to obtain the bicyclic lactone in highenantiomeric purity. Recrystallization or reslurrying allows furtherpurification of this salt. (XXa) can be used as a starting material inthe further synthesis of intermediates (XVIII) and (VIII), as describedabove. The latter in turn can be converted to intermediate (VI), animportant building block in the preparation of the compound of formula(I).

The racemic bicyclic lactone carboxylic acid (XV) is prepared asdescribed in WO 2008/092955 and as outlined above in the schemeillustrating the preparation of (Xa) and (Xb). In particular, (XV) isprepared by reducing the ketocyclopentane biscarboxylic acid (XVII) tothe corresponding hydroxycyclopentane biscarboxylic acid (XVI), whichsubsequently is converted to (XV) by lactone formation. The keto tohydroxy reduction in (XVIII) can be done by hydrogen in the presence ofa noble metal catalyst, e.g. rhodium on carbon (Rh/C) or Raney Ni, in areaction-inert solvent, e.g. in water. The resulting hydroxycyclopentanebiscarboxylic acid (XVI) can be converted to a salt, e.g. a tertiaryamine salt such as the triethylamine salt.

Cyclization via lactone formation of (XVII) can be done by reaction witha chloro-formate, e.g. with ethyl or methyl chloroformate. This reactionis done in a reaction-inert solvent such as a ketone, in particularacetone, or an ether such as THF or MeTHF, or acetonitrile. A base canbe added, e.g. a tertiary amine such as triethylamine

In one embodiment, the present invention relates to the use of thecompounds of formula (XX) or (XXa) as intermediates in the preparationof the compound of formula (I), or the salts thereof.

In another embodiment, the present invention relates to the compoundsper se of formula (XX) or (XXa). These compounds may be in isolatedform, or in solution. In particular, the compounds of formula (XX) or(XXa) are isolated in solid form.

The further processing of the compounds of formula (VIII) to the endproducts of formula (I) are as outlined in the reaction schemes aboveand in particular as outlined in WO 2008/092955. This further processingcomprises a Mitsunobu reaction, which involves the inversion of thestereochemistry of the cyclopentyl carbon bearing the hydroxy group.

The intermediate of formula (VI) is crystallizable, in particular whenmixed with an alcoholic solvent, more in particular when mixed with aC₁₋₄alkanol. Crystallization of the intermediate of formula (VI) allowscontrolling the purity of this compound as well as any compounds derivedtherefrom in subsequent process steps. In particular this propertyallows the preparation of the intermediate of formula (VI) in greaterenantiomeric purity.

This crystallization of intermediate (VI) not only allows to remove theside products of the Mitsunobu reactions that yield these compounds, butalso to subsequently separate intermediate (VI) from its reactionmixtures in a simple way. This separation is easily done by effecting asolvent change, in particular by adding an alcoholic solvent to thereaction mixture obtained from the Mitsunobu reactions, without havingto manipulate any further the reaction mixture or any component thereof.Further, since intermediate (VI) is not soluble in an alcoholic solvent,while the by-products are, this offers immediate purification ofintermediate (VI) from the reaction mixture.

As used in the foregoing and hereinafter, the following definitionsapply unless otherwise noted. The term halo is generic to fluoro,chloro, bromo and iodo. The term “C₁₋₄alkyl” defines straight orbranched chain saturated hydrocarbon radicals having from 1 to 4 carbonatoms such as for example methyl, ethyl, 1-propyl, 2-propyl, 1-butyl,2-butyl, 2-methyl-1-propyl, 2-methyl-2-propyl. “C₁₋₃alkyl” is generic tomethyl, ethyl, 1-propyl, and 2-propyl. “C₁₋₃alkyl” is generic to methyland ethyl. The term C₁₋₄alkanol refers to an alcohol derived from aC₁₋₄alkyl group.

The generally accepted convention for representing stereochemicalcompounds, which is also adhered to herein, is the following:

-   -   A compound represented without stereobonds, e.g. compound (XV),        is racemic or the configuration of the stereogenic center(s) is        not defined.    -   A compound represented with stereobonds and one of the        descriptors “(±)”, “rel”, or “rac”, is racemic and the        stereochemistry is relative.    -   A compound represented with stereobonds but without the        descriptors “(±)”, “rel”, or “rac” refers to a non-racemic        compound (scalemic substance) or an enantio-enriched, i.e. the        stereochemistry is absolute.

For instance, in the Honda et al. reference the designation “(±)” isused in the title of the article, meaning that there is described aracemic synthesis with racemic intermediates. However the aboveconvention may not necessarily be followed in all publications.

The chiral purity is given as enantiomeric ratio (e.r.). For the salts,the e.r. value refers to the ratio of the two enantiomers in thediastereomeric mixture. See for example intermediate (XV).

In certain embodiments, the term “about” when used in relation to anumerical value can be left out so that the exact value is meant. Inother embodiments this term can mean the numerical value to which it islinked ±10%, or ±5%, or ±1%.

EXAMPLES

The following examples are intended to illustrate the present inventionand should not be construed as a limitation of the scope of the presentinvention.

Example 1

To a suspension of 32.7 g (0.19 mol) of intermediate (XVII) (racemic) in237.5 ml water under an atmosphere of nitrogen was added 1.0 ml (0.019mol) 50% wt/wt aqueous NaOH. Warm the mixture to 60° C. and add 2.5 gRh/C (5% wt/wt). The reaction flask was purged with hydrogen and stirredunder an atmosphere of hydrogen until complete conversion was reached.The warm reaction mixture was filtered over Celite. The filter cake waswashed twice with 10 ml water. Triethylamine (55.61 ml, 0.40 mol) wasadded and 80% of the solvent volume was distilled off under a pressureof 30 mbar. The reaction flask was fitted with a Dean-Stark trap filledwith 2-methyl-tetrahydrofuran. 2-Methyltetrahydrofuran (100 ml) wasadded to the reaction mixture, which was refluxed for 4 hours to removethe remaining water. 80% of the solvent volume was distilled off underambient pressure. The mixture was cooled to 50° C. and acetone (380 ml)added. The mixture was cooled further to 22° C. and again acetone (760ml) was added. The resulting suspension was cooled under an atmosphereof nitrogen to −5° C. and triethylamine (27.8 ml, 20.24 g, 0.2 mol) wasadded. Then ethyl chloroformate (22.68 g, 0.21 mol) was added dropwiseand the mixture was stirred at 0° C. for 3 hours. The reaction mixturewas warmed to 22° C. and stirred for a further 12 hours, then filteredover dicalite and the solids were washed with acetone (100 ml). Theresulting solution of (XV) in acetone was used in the following exampleto prepare its cinchonidine salt.

Example 2 Preparation of Cinchonidine Salt (XXa)

Method 1

Approximately 80% of the solvent volume was distilled off underatmospheric pressure. Ethyl acetate (190 ml) was added and the organicsolution was washed with aqueous HCl (2M, 114 ml), yielding a solutionof (XV) in ethyl acetate. The solution of (XV) in ethyl acetate wasadded to a suspension of cinchonidine (55.94 g, 0.19 mol) inacetonitrile (760 ml) at 60° C. The resulting mixture was stirred at 60°C. for 10 minutes and then cooled to 22° C. and filtered. The solidswere recrystallized from isopropanol (1500 ml) to yield after drying24.8 g (29% yield) of a white solid. Chiral purity: e.r.: 89/11

H-NMR (DMSO-d6-400 MHz), δ ppm 1.45-1.86 (m, 6H), 1.93-2.19 (m, 3H),2.32 (br s, 1H), 2.56-2.80 (m, 2H), 2.90-3.07 (m, 2H), 3.12-3.29 (m,1H), 3.30-3.52 (m, 1H), 4.93-5.03 (m, 3H), 5.52 (d, J=5.6 Hz, 1H),5.80-5.89 (m, 1H), 7.5 (d, J=4.2 Hz, 1H), 7.6 (t, J=5.6 Hz, 1H), 8.0 (d,J=9.3 Hz, 1H), 8.3 (d, J=8.1 Hz, 1H), 8.8 (d, J=4.6 Hz, 1H),

Method 2

Approximately 80% of the solvent volume was distilled off underatmospheric pressure. Ethyl acetate (522 ml) was added and approximately50% of the solvent volume was distilled off. The remainder was cooled to22° C. and ethyl acetate (180 ml) was added. The resulting suspensionwas filtered and the filtrate added to a suspension of cinchonidine(55.94 g, 0.19 mol) in acetonitrile (760 ml). This mixture was warmed to60° C., stirred for 10 minutes, then cooled to 22° C. and filtered. Thesolids were recrystallized from isopropanol (1500 ml) to yield afterdrying 24.8 g (29% yield) of a white solid. Chiral purity: e.r.: 90/10

Method 3

Following the procedure of Method 2, but changing the suspension ofcinchonidine (55.94 g, 0.19 mol) in acetonitrile (760 ml) by asuspension of cinchonidine (55.94 g, 0.19 mol) in isopropanol (325 ml)and ethanol (325 ml), there were obtained 24.8 g (29%) of a white solid.Chiral purity: e.r.: 92/8.

The chemical purity of (XXa) as well as the e.r. can be increased byeither recrystallisation or re-slurry of the salts, as described in thefollowing three procedures.

12 g of crude (XXa) (chemical purity: acid titration: 96.2%, basetitration 102.2%; chiral purity: e.r.: 78.7/21.3) was dissolved in 500ml refluxing 2-propanol. The mixture was allowed to cool slowly. If thecrystallisation did not begin spontaneously, the mixture was seeded with(XXa) at 40° C., then stirred at this temperature for 2 hours. Aftercooling to room temperature, the mixture was stirred further for 2hours, filtered and washed with 50 ml of 2-propanol to give, afterdrying in vacuum at 50° C., 5.51 g of white product. Chemical purity:acid titration 99.6%, base titration 98.4%; chiral purity: e.r.:88.1/11.9.

A mixture of 5.3 g (XXa) with e.r. 87.0/13.0 and 0.5 g (XXa) with e.r.:90.6/9.4 was dissolved in 160 ml refluxing ethanol containing 5 wt % ofwater. The clear solution was allowed to cool slowly. If thecrystallization did not begin spontaneously, the mixture was seeded with(XXa) at 45° C. After cooling to room temperature, the mixture wasstirred further for 14 hours, filtered and washed with 10 ml of ethanolcontaining 5 wt % of water to give, after drying in vacuum at 50° C.,4.21 g of white product. Chiral purity: e.r.: 96.5/3.5

A mixture of 25 g (XXa) with e.r. 87.0/13.0 and 2.5 g (XXa) with e.r.:90.6/9.4 was heated to reflux in 160 ml ethanol containing 5 wt % ofwater. After 1 hour at reflux, the slurry was allowed to cool to roomtemperature over 2 hours and stirred further for 14 hours. The mixturewas then filtered and washed with 15 ml of ethanol containing 5 wt % ofwater to give, after drying in vacuum at 50° C., 22.96 g of whiteproduct. Chiral purity: e.r.: 97.6/2.4

Example 3 Preparation of (XVI) and its Triethylamine Salts (XVIa)

(a) 344 mg (2 mmol) (XVII) and 725 mg (4 mmol) tetramethylammoniumhydroxide pentahydrate were dissolved in a mixture of 2.5 ml methanoland 2.5 ml MeTHF. The solution was stirred overnight at room temperatureunder hydrogen atmosphere in the presence of 82 mg wet 5% rhodium oncharcoal as a catalyst. The catalyst was filtered off and the filtratewas diluted to a final volume of 100 ml with methanol. LC analysisshowed that 46.% (XVI) was formed as its bis(tetramethylammonium) saltwhile 41% (XVII) was still present as its bis(tetramethylammonium) salt.

(b) To 400 g of a 6.6 wt/wt % (XVI) solution in water was added 44.4 mltriethylamine 330 g solvent was distilled off under vacuum, then theoily residue was allowed to cool to 50° C. and 51.5 ml acetone was addedthus obtaining a suspension. This suspension was cooled to roomtemperature and 155 ml more acetone was added. The suspension was cooledto 5° C. and stirred overnight at that temperature. The solid wasfiltered, washed with cold acetone and dried at 70° C. under vacuum thusobtaining 15.05 g (XVI) as its complex with various amounts oftriethylamine (XVIa) as a white crystalline powder. Yield: 37%. Forexample (XVI) as its complex with ⅓, or with 2 triethylamine could beobtained.

wherein x is between ⅓ and 3, e.g. x is ⅓; x is 2.

Purification of (XVIa)

(a) 2.00 g crude (XVIa) was suspended in 10.4 ml acetone and thesuspension was brought to reflux before being allowed to cool down toroom temperature. The solid was filtered, washed with acetone and driedat 50° C. under vacuum to give 210 mg pure (XVIa) as a white powder.Yield: 35%.

(b) 2.00 g crude (XVIa) was suspended in 10.4 ml butanol and thesuspension was brought to reflux before being allowed to cool down toroom temperature. The solid was filtered, washed with acetone and driedat 50° C. under vacuum to give 190 mg purified (XVIa) as a white powder.Yield: 14%.

Example 4 Preparation of (XVIII)

(a) 14.18 g (31.5 mmol) (XXa) (e.r.: 90/10), 3.92 g (34.6 mmol) NMHA and8.56 g (34.6 mmol) EEDQ were suspended in 157 ml DCM and the resultingsuspension was refluxed overnight. 47.2 ml methanol was added and thereflux was prolonged overnight. The reaction mixture was thenconcentrated under vacuum and the residue was partitioned between 47 mltoluene and 79 ml aqueous 1M HCl. The organic layer was successivelywashed with 31.5 ml water, 31.5 ml aqueous 1M NaOH and 31.5 ml water,then concentrated under vacuum to give 11.93 g crude (XVIII) (e.r.90/10), which was used without purification in the next step.

(b) 2.50 g (5.55 mmol) (XXa), 691 mg (6.10 mmol) NMHA and 1.51 g (6.10mmol) EEDQ were suspended in 28 ml THF and the suspension was refluxedfor 2 days. 22 ml toluene was added and 28 ml solvent was distilled off.After cooling to 50-60° C., 19.4 ml aqueous 1N HCl was added and the twolayers were separated. The organic layer was washed with 5.6 ml waterthen concentrated under vacuum and the residue was purified by flashchromatography to give 910 mg (XVIII). Yield: 65%.

¹H NMR (CDCl₃, 600 MHz, two rotamers present, ratio 55/45): ppm1.26-1.38 (m, 2H), 1.43-1.60 (m, 2H), 2.01 (m, 2H), 2.07-2.21 (m, 4H),2.86 (s, 3H−minor rotamer), 2.89-2.97 (m, 2H), 2.97 (s, 3H−majorrotamer), 3.21 (ddd, 1H−minor rotamer, J=14.7, 9.1, 5.8 Hz), 3.29 (m,1H−minor rotamer), 3.31 (t, 2H, J=7.6 Hz−major rotamer) 4.87-4.93 (m,2H) 4.96 (d, 1H, J=16.2 Hz) 5.71 (m, 1H).

¹³C NMR (CDCl₃, 150 MHz, two rotamers present): major rotamer: ppm25.86, 26.39, 33.24, 33.94, 35.17, 37.43, 37.97, 45.71, 47.95, 80.67,114.71, 138.26, 170.91, 177.33—minor rotamer: ppm 25.7, 27.72, 33.14,33.69, 34.29, 36.72, 38.02, 46.19, 49.61, 80.64, 115.22, 137.73, 171.17,177.28.

(c) 17.85 g (39.6 mmol) (XXa) (e.r.: 97.6/2.4), 4.71 g (41.6 mmol) and10.78 g (43.6 mmol) EEDQ were suspended in 198 ml MeTHF. The suspensionwas refluxed 2 days then cooled to room temperature. The solid materials(consisting mostly of cinchonidine) was filtered off and rinsed withtoluene. To the combined filtrate were added 40 ml water and 7.14 mlconcentrated HCl. The resulting two layers were separated and theorganic one was washed with 20 ml water, dried over magnesium sulfate,filtered and concentrated under vacuum. The residue was purified bychromatography through silica gel (eluent: ethyl acetate-heptane: 65/35)to give 9.35 g (XVIII) as an oil. Yield: 68%.

Example 5 Preparation of (VIIIa), which is the Intermediate of Formula(VIII) Wherein R¹ is Methyl

(a) 1.05 g (4.2 mmol) (XVIII) was dissolved in 25 mL methanol. 0.014 mL(0.2 mmol) methanesulfonic acid was added and the reaction mixture wasstirred three days at room temperature. The volatiles were removed undervacuum and the residue was redissolved in toluene-aqueous 0.33 M NaOHmixture 15 mL each). The layers were separated and the organic layer wasdried over magnesium sulfate and concentrated under vacuum to give 330mg crude (VIIIa) as an oil (yield: 28%).

(b) 20.0 g (44.4 mmol) (XXa), 5.53 g (48.8 mmol) NMHA and 12.08 g (48.8mmol) EEDQ were suspended in 222 ml methanol. The mixture was refluxedfor 24 hours then 178 ml toluene was added. 250 ml solvents weredistilled off and the resulting suspension was cooled to 30° C. 155 mlaqueous 1M HCl was added and the two layers were separated. The waterlayer was extracted twice with 44 ml toluene. The combined organiclayers were dried over magnesium sulfate and filtered giving 122.78 g of4.1 wt/wt % (VIIIa) solution in toluene. Yield: 40%.

(c) 18.42 g of 4.1 wt/wt % (VIIIa) solution in toluene was concentratedunder vacuum and the residue was purified by flash chromatography(eluent: ethyl acetate-DCM: 15/85) to give 680 mg chemically pure(VIIIa).

(d) 44.06 g (97.8 mmol) (XXa) (e.r.: 92.4/7.6), 12.18 g (107.6 mmol)NMHA and 26.60 g (107.6 mmol) EEDQ were suspended in 490 ml methanol.The mixture was refluxed overnight, then 391 ml toluene was added and750 ml of the solvents were distilled off 156 ml water and 30.8 mlconcentrated HCl were added to the residue. The resulting two layerswere separated and the water layer was extracted with 98 ml toluene,then with 98 ml MeTHF. The combined organic layers were dried overmagnesium sulfate and filtered to give 384 g 3.6 wt/wt % (VIIIa)solution in MeTHF-toluene. Yield: 50%.

(e) 19 g (42.2 mmol) (XXa) (e.r.: 93.4/6.6), 5.01 g (44.3 mmol) NMHA and11.46 g (46.4 mmol) EEDQ were suspended in 210 ml THF. The suspensionwas refluxed overnight, then cooled to room temperature. The solidmaterials (mostly cinchonidine) were filtered off and rinsed with 84 mltoluene. To the combined filtrates were added 42 ml water and 7.6 mlconcentrated HCl. The two layers were separated and the organic layerwas washed with 21 ml water, dried over magnesium sulfate, filtered andconcentrated under vacuum. The residue was dissolved in 84 ml methanol,0.14 ml methanesulfonic acid was added and the solution was stirredovernight at room temperature, then refluxed for 24 h before beingcooled to room temperature. 223 mg sodium carbonate was added and themixture was stirred for 1 hour at room temperature. 295 ml toluene wasadded and 160 ml solvents were distilled off to give 184.9 g of 5.3wt/wt % (VIIIa) solution in toluene. Yield: 82%.

(f) 19 g (42.2 mmol) (XXa) (e.r.: 93.4/6.6), 5.34 g (47.2 mmol) NMHA and12.51 g (50.5 mmol) EEDQ were suspended in 210 ml toluene. Thesuspension was refluxed for 2 days, then cooled to room temperature. Aquantitative analysis showed an in situ yield of 80% of (XVIII). Thesolid materials (mostly cinchonidine) were filtered off and rinsed with42 ml toluene. To the combined filtrates were added 42 ml water and 7.6ml concentrated HCl. The two layers were separated and the organic layerwas washed with 21 ml water then with 21 ml brine and concentrated bydistilling off 206 ml solvents. To the concentrate were added 84 mlmethanol and 0.14 ml methanesulfonic acid. The resulting solution wasstirred overnight at room temperature. 223 mg sodium carbonate was addedand stirring was continued for an additional 1-2 hours. 295 ml toluenewas added and the resulting solid materials were filtered off 183 ml ofsolvents were distilled off to give 180.5 g of 2.7 wt/wt % (VIIIa)solution in toluene. Overall yield of (VIIIa): 41%.

Example 6 Preparation of (VIa), which is the Intermediate of Formula(VI) Wherein R¹ is Methyl

(a) 20.0 g (44.4 mmol) (XXa) (e.r.: 90.1/9.9), 5.53 g (48.8 mmol) NMHAand 12.08 g (48.8 mmol) EEDQ were suspended in 222 ml methanol. Themixture was refluxed for 24 hours, then 178 ml toluene was added. 250 mlsolvents were distilled off and the resulting suspension was cooled to30° C. 155 ml aqueous 1M HCl was added and the two layers wereseparated. The water layer was extracted twice with 44 ml toluene. Thecombined organic layers were dried over magnesium sulfate and filteredgiving 122.78 g of 4.1 wt/wt % (VIIIa) solution in toluene. To 98.22 gof this solution were added 11.17 g (35.5 mmol) (VII) and 9.78 g (37.3mmol) triphenylphosphine and the mixture was cooled to 0° C. 7.4 ml(37.3 ml) DIAD was added dropwise, then the resulting reaction mixturewas stirred at 0° C. for 2 hours during which a precipitate appeared.0.1 ml acetic acid was added and the precipitate was filtered off. Thefiltrate was concentrated under vacuum and the residue was dissolved in71 ml boiling isopropanol. The solution was cooled to 0° C. allowing(VIa) to crystallize. The solid was filtered, washed with coldisopropanol and dried under vacuum to give 6.32 g (VIa) (e.r.:97.2/2.8). Yield from (XXa): 31%.

(b) To 382.8 g of 3.6 wt/wt % (48.6 mmol) (VIIIa) solution inMeTHF-toluene, were added 18.53 g (48.6 mmol) (VII) and 19.7 g (75.4mmol) triphenylphosphine. 118 g of the solvents were distilled off andthe resulting residue was cooled to 0° C. 14.9 ml (75.4 mmol) DIAD wasadded dropwise and the reaction mixture was stirred 2 hours at 0° C. Theresulting solid precipitate (mostly triphenylphosphine oxide) wasfiltered off and washed with cold toluene. 140 g solvents were distilledoff from the combined filtrates, then 97 ml 1-butanol was added and 77 gsolvents were distilled off. The mixture was cooled to 80° C. and 97 mlisopropanol and 2.43 g dicalite were added. After stirring a few minutesat reflux, the mixture was filtered while hot and the resulting filtratewas cooled to 40° C. 14 mg (VIa) was added as seeding material and themixture was cooled to 0° C. After stirring overnight at 0° C., 48 mlisopropanol was added and stirring was continued at 0° C. for 2 hours.(VIa) was isolated by filtration, washed with 9.7 ml cold isopropanoland dried at 70° C. under vacuum. A first portion of 8.77 g (VIa) wasobtained (yield: 28%). The mother-liquors were concentrated under vacuumand the residue was purified by flash chromatography through silicagelto yield a second crop of (VIa) (12.1 g—yield: 43%).

(c) To 58.9 g (8.3 mmol) of 4 wt/wt % (VIIIa) solution in toluene, wereadded 2.86 g (9 mmol) (VII) and 2.29 g (10.2 mmol) triphenylphosphine.The suspension was dried by distilling off 27 ml solvent, then cooled to0° C. 8.7 ml (10.2 mmol) DIAD was added dropwise and the reactionmixture was stirred 1-2 hour at 0° C. The solid materials were filteredoff and rinsed with 4.2 ml toluene. From the combined filtrates, 27 mlsolvent were distilled off 25 ml 1-butanol was added and 25 ml solventswere distilled off. The residue was cooled to 80° C., 25 ml isopropanoland 415 mg dicalite were added, the suspension was refluxed and filteredwhile hot. The filtrate was cooled to 30° C. and 2.4 mg (VIa) was addedas seeding material. The suspension was cooled to 0° C. and stirred atthis temperature overnight. (VIa) was filtered, washed with 2.5 ml coldisopropanol and dried under vacuum, thus obtaining 24.3 g white powder.Yield: 80%.

Structure Formula no.

(XVII)

(XVI)

(XVIa)

(XV)

(XX)

(XXa)

(XVIII)

(VIII) (VIIIa): R¹ = CH₃

(VII)

(VI) (VIa): R¹ = CH₃

1. A process for preparing a compound of formula (VIII), starting froman cinchonidine salt (XXa), which is reacted with N-methyl-hexenamine(NMHA) (XIX) in an amide-forming reaction to yield the bicyclic lactoneamide (XVIII), in which the lactone group is opened to yield the desiredproduct (VIII), as illustrated in the scheme below, wherein R¹ isC₁₋₄alkyl:


2. The process of claim 1 wherein R¹ is methyl.
 3. The process of claim1 or 2, wherein amide-forming reaction is conducted in the presence ofan amide-coupling reagent in a reaction-inert solvent, optionally in thepresence of a base.
 4. The process of claim 3 wherein the solventcomprises halogenated hydrocarbons such as dichloromethane (DCM) orchloroform, ethers such as tetrahydrofuran (THF) or2-methyltetrahydrofuran (MeTHF), alcohols such as methanol or ethanol,hydrocarbon solvents such as toluene or xylene, dipolar aprotic solventssuch as DMF, DMA, acetonitrile, or mixtures thereof.
 5. The process ofclaim 3 wherein the amide forming agent comprises agents such asN-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ),N-isopropoxy-carbonyl-2-isopropoxy-1,2-dihydroquinoline (IIDQ),N,N,N′,N′-tetramethyl-O-(7-azabenzotriazol-1-yl)uroniumhexafluorophosphate (HATU),benzotriazol-1-yl-oxy-tris-pyrrolidino-phosphonium hexafluorophosphate,CDI, 1-ethyl-3-(3-di-methylaminopropyl) carbodiimide (EDCI) or itshydrochloride, dicyclohexyl-carbodiimide (DCC),1,3-diisopropylcarbodiimide, orO-benzotriazole-N,N,N′,N′-tetramethyl-uronium-hexafluorophosphate(HBTU), optionally in the presence of a catalyst such as1-hydroxybenzotriazole (HOBt) or 4-dimethylaminopyridine (DMAP).
 6. Theprocess of claim 3 wherein the optional base is a tertiary amine, suchas triethylamine, N-methylmorpholine, N,N-diisopropylethylamine.
 7. Aprocess for preparing the cinchonidine salt (XXa), which is obtainedfrom the racemic salt (XX) by crystallization:


8. The process of claim 7, wherein the racemic salt (XX) is obtained bycontacting the bicyclic lactone carboxylic acid (XV) with cinchonidine:


9. The process of claim 8, wherein a suspension of cinchonidine is addedto a solution of (XV) at slightly elevated temperature and subsequentlyallowing the mixture to cool whereupon the desired product (XXa)crystallizes.
 10. The process of claim 7 or 8, wherein (XV) is dissolvedin a solvent selected from ester solvents such as ethyl acetate, andsolvents for the cinchonidine suspension include acetonitrile.
 11. Theprocess of claim 9 or 10, wherein the salt formation is done at atemperature of about 50 to about 70° C., in particular at about 60° C.,and the mixture is allowed to cool to about room temperature, such as atemperature in the range from about 20 to about 25° C.
 12. The processof claim 9 or 10, wherein the salt is further purified byrecrystallization from an appropriate solvent or solvent mixture; or byre-slurrying in a solvent or solvent mixture.
 13. The process of claim12, wherein the solvent in the recrystallization is a C₁₋₄alkanol, e.g.isopropanol, or in the re-slurrying the solvent or solvent mixture is anethanol/water mixture such as a 5%/95% (w/w) water/ethanol mixture. 14.The cinchonidine salt of formula


15. The use of the chinochonidine salt (XXa) defined in claim 4, as anintermediate in the preparation of intermediate (VIII).